FieldNameLookup.cs

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using System.Collections;
using System.Data.Common;
using System.Globalization;
 
namespace System.Data.ProviderBase;
 
internal sealed class FieldNameLookup
{
    private Hashtable _fieldNameLookup;
 
    private readonly string[] _fieldNames;
 
    private CompareInfo _compareInfo;
 
    private readonly int _defaultLocaleID;
 
    public FieldNameLookup(IDataRecord reader, int defaultLocaleID)
    {
        int fieldCount = reader.FieldCount;
        string[] array = new string[fieldCount];
        for (int i = 0; i < fieldCount; i++)
        {
            array[i] = reader.GetName(i);
        }
        _fieldNames = array;
        _defaultLocaleID = defaultLocaleID;
    }
 
    public int GetOrdinal(string fieldName)
    {
        if (fieldName == null)
        {
            throw ADP.ArgumentNull("fieldName");
        }
        int num = IndexOf(fieldName);
        if (-1 == num)
        {
            throw ADP.IndexOutOfRange(fieldName);
        }
        return num;
    }
 
    public int IndexOf(string fieldName)
    {
        if (_fieldNameLookup == null)
        {
            GenerateLookup();
        }
        object obj = _fieldNameLookup[fieldName];
        int num;
        if (obj != null)
        {
            num = (int)obj;
        }
        else
        {
            num = LinearIndexOf(fieldName, CompareOptions.IgnoreCase);
            if (-1 == num)
            {
                num = LinearIndexOf(fieldName, CompareOptions.IgnoreCase | CompareOptions.IgnoreKanaType | CompareOptions.IgnoreWidth);
            }
        }
        return num;
    }
 
    private int LinearIndexOf(string fieldName, CompareOptions compareOptions)
    {
        CompareInfo compareInfo = _compareInfo;
        if (compareInfo == null)
        {
            if (-1 != _defaultLocaleID)
            {
                compareInfo = CompareInfo.GetCompareInfo(_defaultLocaleID);
            }
            if (compareInfo == null)
            {
                compareInfo = CultureInfo.InvariantCulture.CompareInfo;
            }
            _compareInfo = compareInfo;
        }
        int num = _fieldNames.Length;
        for (int i = 0; i < num; i++)
        {
            if (compareInfo.Compare(fieldName, _fieldNames[i], compareOptions) == 0)
            {
                _fieldNameLookup[fieldName] = i;
                return i;
            }
        }
        return -1;
    }
 
    private void GenerateLookup()
    {
        int num = _fieldNames.Length;
        Hashtable hashtable = new Hashtable(num);
        int num2 = num - 1;
        while (0 <= num2)
        {
            string key = _fieldNames[num2];
            hashtable[key] = num2;
            num2--;
        }
        _fieldNameLookup = hashtable;
    }
}